The compression and shear induced micro-mechanical interaction of geotextile filaments and geomembrane surface texture elements have been quantified using needle punched nonwoven geotextiles in combination with smooth/textured HDPE geomembrane. A sample preparation method of epoxy resin impregnation followed by optical image analysis was applied to allow the sensitive geotextile microstruc-ture at different stages of interface shear loading to be observed. The changes in geotextile inner structure were statistically quantified in terms of filament nearest neighbor distance distribution and the variations in filament size distributions were quantitatively evaluated under various boundary conditions. The study pro-vides insight into the mechanism of geotextile microstructure evolution under different boundary condi-tions.